Modern data centers often have a multi-tier configuration wherein a front end server accesses one or more layers of middle-tier and back-tier servers for various services. One example of a back-end server is a storage array. Storage arrays form the backbone of modern data centers by providing consolidated data access to multiple applications simultaneously. Increasingly, organizations are moving towards consolidated storage, either using block-based access over a Storage Area Network (SAN) or file-based access over Network-Attached Storage (NAS) systems. A Storage Area Network is a network whose primary purpose is the transfer of data between computer systems and storage elements. Easy access from anywhere at anytime, ease of backup, flexibility in allocation and centralized administration are some of the advantages of storage arrays.
When multiple hosts share a storage array, access to the storage arrays by the different hosts is typically managed. For this purpose, it is desirable to aggregate, amongst the hosts, the input/output (IO) statistics of each host for optimal operational efficiency. According to a method described in U.S. patent application Ser. No. 12/260,041, filed Oct. 28, 2008, the entire contents of which are incorporated by reference herein, a shared file may be used to store the relevant IO statistics of each of the hosts. The shared file is accessed by each of the hosts and updated by each of them in a decentralized manner to reflect their current IO statistics. Shared files also provide the benefit of fault containment.
When a new host is added and configured to have shared access to the storage array, an entry for the new host is added to the shared file. As such, the size of this shared file grows over time as additional hosts are added and configured to have shared access to the storage array. When hosts are taken off-line, the corresponding entries in the shared file should be deleted so that the size of the shared file does not become unreasonably large and IO statistics maintained for such hosts are not used in computing any aggregate IO statistics.